#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#define maxn 110

using namespace std;

int n, m;

int main()
{
    int T; cin >> T;
    while (T -- )
    {
        cin >> n >> m;
        int res = 1e9;
        for (int i = 1; i <= n; i ++ )
        {
            int x, y;
            cin >> x >> y;
            int cost = (m + x - 1) / x * y;
            res = min(res, cost);
        }
        
        cout << res << endl;
    }
    
    return 0;
}